SET QUOTED_IDENTIFIER OFF 
GO
SET ANSI_NULLS OFF 
GO


ALTER   FUNCTION dbo.distance2
	(
		  @StartLatitude float -- Start Latitude
		, @StartLongitude float -- Start Longitude
		, @FinalLatitude float -- Final Latitude
		, @FinalLongitude float -- Final Longitude
	)
RETURNS @tbl TABLE (Distance float, Bearing float)
AS
	BEGIN
DECLARE
	  @fPhimean float -- Mean Latitude
	, @fdLambda float -- Difference between longtitudes
	, @fdPhi float -- Difference between lantitudes
	, @fAlpha float -- Drift
	, @fRho float -- Meridian radius of curvature. 
	, @fNu float -- Cross-section radius of curvature
	, @fR float -- Earth radius
	, @fz float -- Angular distance from the center of a spheroid
	, @fTemp float -- The temporal variable used in calculations
	, @Distance float -- Distance in meters
	, @Bearing float -- Bearing
	, @R2D float --  constant for transformation a radian in degrees
	, @a float -- The basic halfaxes
	, @b float -- Nonbasic halfaxes
	, @e2 float -- A square of ellipsoid eccentricity
	, @f float -- Alignment of ellipsoid


	SET @R2D =  57 . 295781 
	SET @a =  6378137 . 0 
	SET @b =  6356752 . 314245 
	SET @e2 =  0 . 006739496742337 
	SET @f =  0 . 003352810664747 


	-- We calculate a difference between two longitudes and breadthes and it is received average breadth 
	SET @fdLambda = radians(@StartLongitude - @FinalLongitude);
	SET @fdPhi = radians(@StartLatitude - @FinalLatitude);
	SET @fPhimean = radians((@StartLatitude + @FinalLatitude) /  2 . 0 );

	-- We calculate meridian and cross-section radiuses of curvature of average breadth 
	SET @fTemp =  1  - @e2 * (Power(Sin(@fPhimean),  2 ));
	SET @fRho = (@a * ( 1  - @e2)) / Power(@fTemp,  1 . 5 );
	SET @fNu = @a / (Sqrt( 1  - @e2 * (Sin(@fPhimean) * Sin(@fPhimean))));

	-- We calculate angular distance 
	SET @fz =
		Sqrt(Power(Sin(@fdPhi /  2 . 0 ),  2 ) + Cos(radians(@FinalLatitude)) * Cos(radians(@StartLatitude)) *
		Power(Sin(@fdLambda /  2 . 0 ),  2 ));

	SET @fz =  2  * ASin(@fz);

	-- We calculate displacement 
	SET @fAlpha = Cos(radians(@FinalLatitude)) * Sin(@fdLambda) *  1  / Sin(@fz);
	SET @fAlpha = ASin(@fAlpha);

	-- We calculate radius of the Earth 
	SET @fR = (@fRho * @fNu) / ((@fRho * Power(Sin(@fAlpha),  2 )) + (@fNu *
		Power(Cos(@fAlpha),  2 )));

	-- Calculating displacement and distance 
	SET @Distance = (@fz * @fR);
	if ((@StartLatitude < @FinalLatitude) and (@StartLongitude < @FinalLongitude))
		SET @Bearing = Abs(@fAlpha * @R2D)
	else if ((@StartLatitude < @FinalLatitude) and (@StartLongitude > @FinalLongitude))
		SET @Bearing =  360  - Abs(@fAlpha * @R2D)
	else if ((@StartLatitude > @FinalLatitude) and (@StartLongitude > @FinalLongitude))
		SET @Bearing =  180  + Abs(@fAlpha * @R2D)
	else if ((@StartLatitude > @FinalLatitude) and (@StartLongitude < @FinalLongitude))
		SET @Bearing =  180  - Abs(@fAlpha * @R2D);

		INSERT INTO @tbl (Distance, Bearing)
		SELECT @Distance, @Bearing
	RETURN
	END


GO
SET QUOTED_IDENTIFIER OFF 
GO
SET ANSI_NULLS ON 
GO